4 Myron Harmon Swenk 
The importance of these has been admirably brought out by Rev. 
F. D. Morice in his study of thirty-four palaearctic species 
(Transactions of the Entomological Society of London, 1904, 
pp. 25-03), especially in the case of the seventh ventral plate. 
Concerning this structure he says: ‘The seventh ventral plate 
is a most interesting and surprising object. Its base is a ribbon- 
like strip or arch of chitin, joined at each end to the correspond- 
ing dorsal plate. Springing from the apex of this arch appear 
nearly always two large symmetrical lobes or ‘wings.’ They are 
perfectly colourless and membranous at the extreme apex, still 
membranous, but more or less infuscated, punctured, and pilose 
on the disc, evidently chitinized at the base and along the inner 
margin, and at least somewhat thickened and darkened on the 
exterior margin. . . The form, colour arid pilosity of these 
lobes differ specifically to such an extent, that many species can 
be distinguished at a glance by these characters alone. Not only 
the actual outlines, but even the minute veinings, cloudings, ete. 
of the membrane seem to be extremely constant. . . I have 
frequently dissected many specimens of one species from widely- 
different localities, and have nearly always found their seventh 
segments exactly similar, and quite unlike that of any other spe- 
cies. The cases in which two different species have this plate 
deceptively similar, are extremely rare; and curiously enough, 
where this does happen, the insects themselves are very unlike 
each other in external characters. . . It is perfectly easy, with 
a little practice,'so to prepare either fresh or relaxed specimens 
as to display this segment sufficiently for all practical purposes ; 
or it can be actually removed and mounted separately without any 
noticeable disfiguring of the specimen, but in that case the liga- 
ments connecting it with the dorsal plate must be severed cau- 
tiously first.” In order to thoroughly test the constancy of the 
form and pilosity cf this plate the writer dissected forty odd spec- 
imens of C. inaequalis, and found the plate exactly the same in 
all. 
Along with the seventh ventral plate the armatures themselves 
present specific characters of great value, but because of their 
more complex structure are of less practical use in this connec- 
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